1. Field of the Invention
This disclosure is related to the field of polymer interlayers for multiple layer panels and multiple layer panels having at least one polymer interlayer sheet. Specifically, this disclosure is related to the field of stabilized fluorescent particles for use in polymer interlayers and polymer interlayers comprising stabilized fluorescent particles.
2. Description of Related Art
Multiple layer panels are generally panels comprised of two sheets of a substrate (such as, but not limited to, glass, polyester, polyacrylate, or polycarbonate) with one or more polymer interlayers sandwiched therebetween. The laminated multiple layer glass panels are commonly utilized in architectural window applications and in the windows of motor vehicles and airplanes. These applications are commonly referred to as laminated safety glass. The main function of the interlayer in the laminated safety glass is to absorb energy resulting from impact or force applied to the glass, to keep the layers of glass bonded even when the force is applied and the glass is broken, and to prevent the glass from breaking up into sharp pieces. Additionally, the interlayer may, among other things, give the glass a much higher sound insulation rating, reduce UV and/or IR light transmission, and/or enhance the aesthetic appeal of the associated window. The interlayer may be a single layer, a combination of two or more single layers, a multilayer that has been coextruded, a combination of at least one single layer and at least one multilayer, or a combination of multilayer sheets. In regard to the photovoltaic applications, the main function of the interlayer is to encapsulate the photovoltaic solar panels which are used to generate and supply electricity in commercial and residential applications.
Laminated safety glass, or multiple layer glass panels, is used in many different applications in the transportation industry, including automotive, railroad, and aviation vehicles. Polymer interlayers used in laminated safety glass have also been used as an important component in transportation vehicles, such as in automobile head-up display (HUD) systems, which can provide, for example, an instrument cluster image at the eye level of a driver of the vehicle, such as an automobile, or in the cockpit of an airplane. Such a display allows a driver to stay focused on the road in front of him while visually accessing important dash board information. One type of interlayer used in such head-up display systems is an interlayer that is wedge shaped in vertical cross section. The wedge shape of the interlayer is used to provide the correct light dynamics through the windshield required for a head-up display. While the wedge shaped interlayer is effective to provide the correct light dynamics, the wedge shaped interlayer is sometimes difficult to handle during processing due to the different thicknesses across the cross section. When wound onto a core, one side of the roll (where the thickness is greatest) is larger than the other side, or when cut windshield blanks are stacked, one side of the stack is thicker or higher than the other side due to the thicker wedge section.
Head-up displays have also been widely used in aviation applications. The systems mounted in the direct field of vision of pilots display the most important data about their own and other aircraft. These systems, established and much used in the military sector, also have many possibilities for use in the civil sector, in particular in the automobile sector. Thus, data about the speed, the distance from the preceding vehicle or directional data from the navigation equipment can be displayed right at the eye level of the driver. These possibilities clearly improve the traffic safety of the vehicle as the driver cannot watch the traffic situation while looking at the instruments. With increased speeds of the motor vehicle, on freeways, for example, the distance traveled “blind” by the vehicle can be significant and can cause an increased accident rate. There is a need for improved interlayers for use in windshields having head-up displays.
Interlayers for windshields and other multiple layer glass panel applications are generally produced by mixing a polymer resin (or resins) such as poly(vinyl butyral) with one or more plasticizers and other additives and melt processing the mix into a sheet by any applicable process or method known to one of skill in the art, including, but not limited to, extrusion. For multiple layer interlayers comprising two or more layers, the layers may be combined by processes such as co-extrusion and lamination. Other additional ingredients may optionally be added for various other purposes. After the interlayer sheet is formed, it is typically collected and rolled for transportation and storage and for later use in the multiple layer glass panel, as discussed below.
Contemplated polymer interlayers include, but are not limited to, poly(vinyl)acetal resins such as poly(vinyl butyral) (PVB), polyurethane (PU), poly(ethylene-co-vinyl acetate) (EVA), polyvinylchloride (PVC), polyethylenes, polyolefins, ethylene acrylate ester copolymers, poly(ethylene-co-butyl acrylate), silicone elastomers, epoxy resins and any acid copolymers and ionomers derived from any of the foregoing possible thermoplastic resins. Multilayer laminates can include multiple layer glass panels and multilayer polymer films. In certain embodiments, the multiple polymer films in the multilayer laminates may be laminated together to provide a multilayer film or interlayer. In certain embodiments, these polymer films may have coatings, such as metal, silicone or other applicable coatings known to those of ordinary skill in the art. The individual polymer films which comprise the multilayer polymer films may be laminated together using an adhesive as known to those of ordinary skill in the art.
The following offers a simplified general description of the manner in which multiple layer glass panels are generally produced in combination with the interlayers. First, at least one polymer interlayer sheet (single or multilayer) is placed between two substrates and any excess interlayer is trimmed from the edges, creating an assembly. It is not uncommon for multiple polymer interlayer sheets or a polymer interlayer sheet with multiple layers (or a combination of both) to be placed within the two substrates creating a multiple layer glass panel with multiple polymer interlayers. Then, air is removed from the assembly by an applicable process or method known to one of skill in the art; e.g., through nip rollers, vacuum bag or another deairing mechanism. Additionally, the interlayer is partially press-bonded to the substrates by any method known to one of ordinary skill in the art. In a last step, in order to form a final unitary structure, this preliminary bonding is rendered more permanent by, for example, a high temperature and pressure lamination process known to one of ordinary skill in the art such as, but not limited to, autoclaving, or by other processes known to one of ordinary skill in the art.
One of the problems in the manufacture of multilayer laminate glass panels is the presence of various optical defects in the final unitary structure or laminate, such as the windshield or panel. The multiple layer glass panels need to be free of optical defects and have good clarity (or low haze values) to allow for clear vision through the glass panels. Additionally, the multiple layer glass panels need to be aesthetically pleasing, that is, the glass panels cannot have a high level of undesirable color, such as yellow color. It is important to maintain the high optical clarity standards when adding new features and functionality to the glass panels.
Optical quality defects such as haze or lack of clarity and increased color or yellowness are common problems in the field of multiple layer glass panels. Good optical quality is particularly important where the multiple layer glass panels are those used in applications which require higher levels of optical or visual quality, such as windshields. This is even more important for windshields or other multiple layer glass panels where head-up displays or other features are used. In an attempt to improve the multiple layer glass panels used in windshields and other glazing applications, and particularly those used with head-up displays, new technology has been developed to provide improved head-up displays. One attempt to improve the technology is the use of fluorescent or luminescent pigments in the windshield. Using a fluorescent or luminescent pigment based head-up display has potential advantages over head-up displays that use wedge shaped interlayers, such as easier and more efficient polymer interlayer production, handling and storage, as well as improved lamination capabilities. However, the use of the fluorescent pigments results in other unfavorable sacrifices, including, but not limited to, uneven distribution of the pigments on and/or in the interlayer, poor optical quality (i.e., increased color and haze in the laminate), visual defects, poor (too high or too low) adhesion, increased manufacturing costs (i.e., the costs associated with producing the multilayer interlayer as well as the cost of the pigment). Accordingly, there is a need in the art for the development of an interlayer that can be used in head-up display applications and has excellent optical and other properties, such as an interlayer that resists or prevents the formation of color or yellowness and an increase in haze (or reduction in clarity) without a reduction in other optical, mechanical, and performance characteristics of a conventional interlayer.